A conventional thrust roller bearing 101 is disclosed in Japanese Unexamined Patent Publication No. 2003-83339, for example. Referring to FIG. 29, the thrust roller bearing 101 disclosed in the above document includes a plurality of rollers 102, a retainer 103 to retain the plurality of rollers 102, and first and second track rings 104 and 105 to sandwich the rollers 102 in a thickness direction.
The first track ring 104 has a track surface 104a formed on one side of a wall surface of an annular member in a thickness direction so as to be in contact with a roller 102, a cylindrical flange part 104b extending from an outer edge part of the annular member toward the side of the track surface 104a, and a plurality of projection parts 104c projecting from a tip end of the flange part 104b toward a radial inner side to hold the retainer 103.
Similarly, the second track ring 105 has a track surface 105a formed on one side of a wall surface of an annular member in a thickness direction so as to be in contact with the roller 102, a cylindrical flange part 105b extending from an inner edge part of the annular member toward the track surface 105a, and a plurality of projection parts 105c projecting from a tip end of the flange part 105b toward a radial outer side to hold the retainer 103.
According to the thrust roller bearing 101, an inner diameter dimension of the flange part 104b is set so as to be larger than an outer diameter dimension of the retainer 103, and a radial bearing internal gap is provided between the retainer 103 and the flange part 104b. Thus, according to the above document, even when the thrust roller bearing 101 is used in circumstances such as a torque converter in which eccentric rotation is generated, heat generation and abrasion due to friction between the retainer 103 and the flange part 104b can be effectively prevented.
Here, as the bearing internal gap is provided, the retainer 103 and the track ring 104 could be separated. For example, they could be separated in the case where the track rings 104a and 105b are transported in a vertical state. Thus, according to the thrust roller bearing 101 disclosed in the above document, a diameter of a circle formed by tip ends of the projection parts 104c is set so as to be smaller than the outer diameter dimension of the retainer 103. Thus, it is reported that the separation between the retainer 103 and the track ring 104 can be prevented. This is applied to the case where the retainer 103 is incorporated in the second track ring 105.
In addition, similar thrust roller bearings are also disclosed in Japanese Unexamined Patent Publication No. 9-137824, Japanese Unexamined Patent Publication No. 9-189325, Japanese Unexamined Patent Publication No. 2000-266043, and Japanese Unexamined Patent Publication No. 2003-254327.
However, as the projection amount of the projection part 104c is increased, assembling properties of the thrust roller bearing 101 deteriorate. More specifically, the retainer 103 and the projection part 104c have to be largely elastically-deformed when going through the projection 104c. This could cause the deformation of the retainer 103 and the damage of the projection part 104.
As one method to solve this problem, the projection part 104c is subjected to an anti-carburizing process so as not to be affected by quenching, or it is subjected to a partial tempering process after a quenching process. However, while the retainer 103 can be easily incorporated due to the above processes, the strength of the projection part 104c is lowered.
In addition, as an alternative method, the thrust roller bearing 101 is subjected to a heat treatment as a whole after the rollers 102 and the retainer 103 have been incorporated in the track ring 104. However, each of the retainer 103 and the track ring 104 is deformed in some cases, which could cause the rotation defect of the thrust roller bearing 101.